Zhejiang Education Press Chapter 2 Section 1

Zhejiang Education Press Chapter 2 Section 1

Foundation and consolidation
1. Have growth and development, need nutrition, have response to stimulation
2. (1) plants
(2) . animals
3.D
4.B
5.A
6.C
7. Feeding and nutrition of animals
After touching, the leaves of Mimosa were closed and stressed
Flowering and fruiting propagation of plants
Mushrooms grow up in small size
8.D
9.C
10.D
Development and improvement
A: column: wood is a plant, and when it is made into paper, it is also abiotic
12. Answer: column: Animals: birds, chickens, dogs, whales, monkeys
Plants: aquatic plants, Rhododendron, cactus, cucumber, pine
Write the following, the answer is not unified!
13. Incorrect, write the reason yourself! There is no unified answer!
Give me 20 points! Tired! I'm just in eighth grade. I also have this one, which has been corrected by the teacher. Believe it or not, it's up to you to choose!

Solving equations: 2 / (x + y) + 5 / (X-Y) = 18 9 / (x + y) - 10 / (Y-X) = 66

Another a = 1 / (x + y), B = 1 / (X-Y); then 2A + 5B = 18; 9A + 10B = 66; the solution is a = 6, B = 6 / 5; that is & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 1 / (x + y) = 6 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp

Use the method of addition and subtraction to solve the following equations: 3 (x + y) - 4 (X-Y) = - 18, 2 / 2 (x + y) + 6 / 6 (X-Y) = 2~

3(x+y)-4(x-y)=-18 ①
(x+y)/2+(x-y)/6=2 ②
3 (x + y) + (X-Y) = 12 (3)
③ - 1
5(x-y)=30
x-y=6④
④ Substituting ③
3(x+y)+6=12
x+y=2⑤
④+⑤
2x=8
x=4
⑤-④
2y=-4
y=-2
The solution of the equation is
{x=4
y=-2

When practicing solving the equations ax + y = 10x + by = 7, because of carelessness, a misread a in the equations and got the solution of the equations as x = 1y = 6; B misread B in the equations and got the solution of the equations as x = - 1y = 12. How much is the solution of the original equations?

Substituting x = 1, y = 6 into the second equation: 1 + 6B = 7, the solution: B = 1, substituting x = - 1, y = 12 into the first equation: - A + 12 = 10, the solution: a = 2, the equation system is 2x + y = 10, ① x + y = 7, ②, ① - ② is x = 3, substituting x = 3 into ② is y = 4, then the solution of the equation system is x = 3Y = 4

To solve the equations {x (x + y + Z) = 6, y (x + y + Z) = 12, Z (x + y + Z) = 18, it is clear

Let P = x + y + Z
Then the equations are changed into:
x=6/p,y=12/p,z=18/p
Substituting the above formula, there is: P = 6 / P + 12 / P + 18 / P
That is, P = 36 / P
p^2=36
We get: P = 6 or - 6
When p = 6, x = 1, y = 2, z = 3
When p = - 6, x = - 1, y = - 2, z = - 3
So there are the above two sets of solutions (1,2,3), (- 1, - 2, - 3)

X / 2 = Y / 3 = Z / 4 x + y + Z = 18 solving equations

Let X / 2 = Y / 3 = Z / 4 = K
Then x = 2K, y = 3k, z = 4K
The original equation becomes 2K + 3K + 4K = 18
So k = 2
Then x = 4, y = 6, z = 8

Solving equations X / 2 = Y / 3 = Z / 4 x + y + Z = 18
Help me solve this system of equations,
｛X/2=Y/3=Z/4
｛X+Y+Z=18

Let z = 4A, then y = 3A, x = 2A, bring in the following formula
9a=18
a=2
therefore
Z=8
Y=6
X=4

The number of solutions of the equations | x | + y = 12, x + | y | = 6 is ()
A、1 B、2 C、3 D、4

Let x > = 0
The equations can be reduced to
x+y=12
x+|y|=6
∴y-|y|=6
unsolvable
Let X

The solution of X + Y / 3 + X-Y / 2 = - 6, 3 (x + y) + 2 (x-2y) = - 12 equations by addition and subtraction method

From (1)
2x+2y+3x-3y=-36
5x-y=-36 (3)
From (2)
3x+3y+2x-4y=-12
5x-y=-12 (4)
From (3) and (4) two equations, there is no solution
Next, change (2) to 3 (x + y) + 2 (X-Y) = - 12
From (1)
2x+2y+3x-3y=-36
5x-y=-36 (3)
From (2)
3x+3y+2x-2y=-12
5x+y=-12 (4)
(3) + (4) get
10x=-48
x=-4.8
(4) - (3) get
2y=24
∴y=12
∴x=-4.8
y=12

X / 6 + Y / 12 = 0.5 ① x + y = 4.8 ② solve the equations

① 12 (x / 6 + Y / 12) = 0.5 × 12 → 2x + y = 6
① - 2 = 2x + Y - (x + y) = 6-4.8 → x = 1.2
2 + y = 4.8 → y = 3.6